This invention relates to a process for preparing a dressing or covering for wounds and/or burns. Animal tissue has long been known to be a useful source of material for wound coverings. Although not identical to human skin, the composition and usefulness of some animal tissue resembles human skin. For example, a covering for wounds, ideally, both protects the wound against contact with moisture and external contaminants, while also being permeable to the excretions, in particular, water vapor, which are produced by normal metabolic processes.
Silver sulfadiazine (AgSD) is known as a useful antimicrobial in the treatment of wounds, and of burns in particular, see U.S. Pat. No. 3,761,590 (1973), Fox; Bose, Storing Amniotic Membrane in Silver Sulfadiazine Suspension, The Canadian Medical Assocation Journal, 127, No. 2, p. 112 (July 15, 1982); Fox, Modak and Stanford, Silver Treated Graft Materials for Coverage of Infected Burn Wounds, Ann. Chir. Plast. 24, N.3, 265-267 (1979).
While animal tissue, and pigskin in particular, satisfies certain criteria for a burn wound covering, there are certain difficulties which militate against using simple, untreated animal tissue as a wound covering. First, and most important of these, is the fact that while animal tissue, when used as a wound covering, may protect the wound against external agents and influences, it does not and cannot prevent infection caused by bacteria, for example, which may have entered the wound prior to the application of the covering, or against whatever bacteria which may enter through the covering. While the problem may be alleviated in part by using a topical bacteriocide (e.g., silver sulfadiazine cream) applied to the skin covering, there is still a chance of infection entering the wound when the dressing must be changed. Such changes must be done with some frequency as the wound cover, even though permeable, will tend to become sodden from topical bacteriocides as well as from metabolic waste products. These changes of dressing allow bacteria to enter, even if the wound is left uncovered for a very short time. Also, while animal tissue is carefully treated so as to attempt to insure that the tissue is initially free of bacteria, sterility cannot be guaranteed, particularly when applied as a wound covering. In particular, should the wound be allowed to be exposed to air, the chance of infection by airborne bacteria is made even greater.